The effect of unilateral stellate ganglion stimulation and isoproterenol on the T wave in dogs will be correlated with local intramyocardial T waves and temperatures, and with electrolyte (K, Na, Ca, Mg) gradients determined by chemical analysis of hearts frozen at the height of the T wave changes. The effect of selectively changing intracellular or extracellular K and Na on the trans-membrane action potentials and T waves will be studied in myocardial cell cultures from chicken embryos. Work will be continued on a more extensive basis on correlation of T wave changes appearing during oral potassium loading in patients with functional and organic T wave abnormalities with the results of the exercise test, the K concentration in the serum and red blood cells, and with electrical body conductivity. Work will be continued with correction of QRS and T wave amplitudes by precordial calibration for assessment of body conductivity during routine electrocardiography.